Wireless signal strength varies according to how far a wireless communication device is away from its access point. Including RF interfaces such as cellular or Wi-Fi, the quality of a wireless link may be impacted by radio noise and obstructions to line of sight. The strength of a wireless link's signal is measured when received by a wireless communication device or a base station. The received signal strength is correlated to the overall quality of a media session, but signal strength is not the only factor that determines session quality. A high quality session has few transmission failures, such as lost or late payload or retransmissions.
In various wireless communication devices such as mobile phones, signal strength is displayed bars. A displayed signal strength indicates the strength of the wireless link between the device and its access point. In various scenarios the signal strength of the connecting wireless link is insufficient to indicate the quality of a media session. The counter-party on the other side of the call may also be connected wirelessly, in which case the session quality may depend on conditions of two wireless networks. Congestion on a backhaul or backbone may also impact session quality.